Effect of Surface Friction on Printing Force of PS Plate

The strength of printing plates affects the production cost. One offset PS plate is generally resistant to printing force of 100,000, and the high-temperature baking of the PS plate can withstand up to 20 squares. Offset PS plate graphic parts and blank parts are almost in the same plane, graphic parts only 3μm higher than the blank part. If the pressure is too high during printing, the plate will be subject to friction and wear, resulting in reduced printing plate resistance.

Let's take a look at the effect of friction on the blank part of the PS version. The hydrophilic foundation of the blank part of the PS plate is sand, which not only can absorb and store enough water to prevent the ink from invading, but also helps the chemical components in the fountain solution to promptly supplement and restore the already lost hydrophilic inorganic salt layer and Hydrocolloid layer. The blank part of the printing plate is gradually worn out during printing, and its wear is mainly divided into three stages. The first stage occurred at the beginning of the new version, showing that the top of the sand was gradually worn out. However, the impact on the print quality is not obvious at this time. In the second stage, the central part of the sand has been worn out and the surface reflection of the printing plate has gradually increased; the amount of “water” stored in the blank part of the printing plate in the third stage has been drastically reduced, and the sand is basically flattened. The stability of the hydrophilic inorganic salt layer and the hydrophilic colloid layer is destroyed, and the blank portion of the PS plate gradually loses hydrophilicity.

Generally, when installing and adjusting the circumferential position of the three rollers of the offset printing machine, the opening of the blanket cylinder should be slightly lagging behind that of the plate cylinder in the circumferential direction. The purpose is to prevent the plate entrance from being received first in each printing cycle. The impact and friction make the grain of the sandstone smooth and bright, which affects the quality of the printed product.

Let's talk about the impact of friction on the graphic part of the printing plate. The graphic part of the plate is generally composed of dots. The wear and tear of high-profile areas will cause the foundation of the network to be destroyed to varying degrees, and gradually generate hydrophilic inorganic salt layer and hydrophilic colloid layer under the action of the fountain solution, making the high-profile nodes more detailed and incomplete. Until the final disappearance, there was a "flower pattern" failure in the printed product. In the low-key area, on the contrary, the area of ​​the graphic part is larger than the area of ​​the blank part. Once the area suffers from friction, the blank part of the blank area will be flattened and will gradually lose its hydrophilicity, resulting in irregular expansion of the low-profile area network, resulting in India. The product has a "burn-in" fault.

In summary, understand the impact of surface friction on the PS version, and take appropriate measures to avoid such failures during the printing process. For example, select the appropriate printing plate, implement “Sanping”, “Sanqin” and “Three Small” standard operations, and reasonably adjust the distribution printing pressure to ensure the printing quality and reduce the production cost.


Source: China Art and Design Alliance